A water drain valve is known from DE 60 2005 002 184 T2, in which the water box drain channel ends largely horizontally and sealingly presses a plastic lip fixed at the top in a tiltable manner against the edge of the drain channel. On its outside the plastic lip comprises a bead, the weight and lever arm of that presses the plastic lip into the position that closes off the drain channel. Through onflowing water, the plastic lip can lift off the edge, thus making possible the outflow of the water. Following this, it closes again under the effect of its own weight, i.e., mainly of the bead weight.
At least one object is to provide a structurally compact and simple water drain valve, which can be used under the cramped conditions in the engine compartment of modern motor vehicles, which furthermore makes possible a reliable sealing with respect to gases, in particular exhaust gases and which reliably discharges the water out of the water box. In addition, other objects, desirable features and characteristics will become apparent from the subsequent summary and detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background.